How to capture freight costs for material

Friends,

I have a Purchase order with 3 line items. I am creating shipment and shipment cost document for only one line item.

But when I do a goods receipt, the shipments costs gets divided equally to all 3 lines items in the PO.

Ideally shipment costs should be assigned to only line item of material cost

Kindly advise how to apportinate the shipment cost only to the items which i receive and not equal distribution?

I am maintaining the frieght condition type in the PO without value to copy the shipment costs

In case of any queries, please revert.

Thanks

Shankar